Nozzle for low pressure flash tanks for ore slurry

• US 6,482,250 B1
• Filed: 02/28/2000
• Issued: 11/19/2002
• Est. Priority Date: 04/17/1998
• Status: Expired due to Fees

• Current Assignee: Barrick Gold Corporation
• Original Assignee: Barrick Gold Corporation
• Inventors: Williams, Richard, Dixon, David, Enloe, Larry, Wilmot, Paul
• Primary Examiner(s): KASTLER, SCOTT R
• Application Number:
  US09/513,945
• Time in Patent Office: 995 Days
• Field of Search: 757/44, 266/168
• US Class Current: 75/744
• CPC Class Codes: C22B 11/12 Apparatus therefor
• CPC Class Codes: C22B 3/02 Apparatus therefor
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry. The nozzle has an expansion cone flaring toward the discharge end of the nozzle. The cross-sectional area of a choke section of the nozzle and the exit diameter of the expansion cone are selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that underflashing, overflashing, and shock waves inside the flash tank are minimized.

Claims

1. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising an inlet end, a discharge end, a tubular passageway extending therebetween for passage of the slurry from a location outside the flash tank in fluid flow communication with said inlet end, the slurry passageway comprising a choke comprising a zone of the passageway in which its cross-sectional area is smallest, the passageway flaring with respect to the axis thereof toward said discharge end to define an expansion cone;

and

the cross-sectional area of the choke and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle consisting of a straight choke.

2. The nozzle of claim 1 wherein the cross-sectional area of the choke and the exit diameter of the expansion cone are selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that under a flowrate of up to about 500 tons per hour of ore slurry comprising between about 30% and about 70% solids by weight, shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle consisting of a straight choke.

3. The nozzle of claim 2 wherein the expansion cone has a half angle of between about 20°

and about 32°

, and the choke cross-sectional area is determined by a function relating mass flow rate of slurry through the nozzle and pressure within the nozzle.

4. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising an inlet end, a discharge end, a tubular passageway extending therebetween for passage of the slurry from a location outside the flash tank in fluid flow communication with said inlet end, the slurry passageway comprising a choke comprising a zone of the passageway in which its cross-sectional area is smallest, the passageway flaring with respect to the axis thereof toward said discharge end to define an expansion cone;

the cross-sectional area of the choke and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle consisting of a straight choke; and

wherein the choke has a diameter between about 2.8 inches and about 4.6 inches, the expansion cone exit diameter is between about 7.7 inches and about 11.5 inches, and the expansion cone length is between about 4 and about 8 inches.

5. The nozzle of claim 4 wherein the expansion cone has a half angle of between about 20°

and about 32°

.

6. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising an inlet end, a discharge end, a tubular passageway extending therebetween for passage of the slurry from a location outside the flash tank in fluid flow communication with said inlet end, the slurry passageway comprising a choke comprising a zone of the passageway in which its cross-sectional area is smallest, the passageway flaring with respect to the axis thereof toward said discharge end to define an expansion cone;

and

the cross-sectional area of the choke and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle consisting of a straight choke;

wherein the nozzle has a choke diameter of between about 3½ and

about 4½

inches, an expansion cone exit diameter of between about 7 and about 7½

inches, and an expansion cone length of between about 5¾

inches and about 6¼

inches.

7. The nozzle of claim 6 wherein the expansion cone has a half angle of between about 14°

and about 16°

.

8. A process for reducing the pressure of pressure oxidized ore slurry from above about 100 psig to about atmospheric, the process comprising passing up to about 500 tons per hour ore slurry comprising between about 30% and about 70% solids by weight through a nozzle into a flash tank, the nozzle disposed on the top of the flash tank and comprising an inlet end and a discharge end, and a slurry passageway extending through the nozzle from the inlet end to the discharge end for passage of the slurry into the flash tank from a location outside the flash tank, the slurry passageway comprising a choke comprising a zone of the passageway in which its cross-sectional area is the smallest, the passageway flaring with respect to the axis thereof toward said discharge end to define an expansion cone, the choke cross-sectional area is determined by a function relating mass flow rate of slurry through the nozzle and pressure within the nozzle, and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle consisting of a straight choke.

13. The process of claim 8 wherein the flash tank comprises a vapor outlet for steam generated therein and a liquid outlet for cooled slurry, the configuration of said tank and the position of said nozzle being such that, under slurry flashing conditions:

the discharge end of said nozzle is spaced above the level of ore slurry in the tank, and the spacing of said discharge end from said slurry level and the depth of the slurry in the tank are sufficient to preclude substantial erosion of the bottom wall of the tank by the impact of slurry entering and flashing within the tank;

the head space above the ore slurry level and the horizontal cross-section of the tank are sufficient for vapor/liquid disengagement; and

the depth of said ore slurry is sufficient to provide a liquid seal for said cooled slurry outlet.

9. A process for reducing the pressure of pressure oxidized ore slurry from above about 100 psig to about atmospheric, the process comprising passing up to about 500 tons per hour ore slurry comprising between about 30% and about 70% solids by weight through a nozzle into a flash tank, the nozzle disposed on the top of the flash tank and comprising an inlet end and a discharge end, and a slurry passageway extending through the nozzle from the inlet end to the discharge end for passage of the slurry into the flash tank from a location outside the flash tank, the slurry passageway comprising a choke comprising a zone of the passageway in which its cross-sectional area is the smallest, the passageway flaring with respect to the axis thereof toward said discharge end to define an expansion cone, the choke cross-sectional area is determined by a function relating mass flow rate of slurry through the nozzle and pressure within the nozzle, and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle consisting of a straight choke;

wherein the choke has a diameter between about 2.8 inches and about 4.6 inches, the expansion cone exit diameter is between about 7.7 inches and about 11.5 inches, and the expansion cone length is between about 4 and about 8 inches.

10. The process of claim 9 wherein the expansion cone has a half angle of between about 20°

and about 32°

.

11. A process for reducing the pressure of pressure oxidized ore slurry from above about 100 psig to about atmospheric, the process comprising passing up to about 500 tons per hour ore slurry comprising between about 30% and about 70% solids by weight through a nozzle into a flash tank, the nozzle disposed on the top of the flash tank and comprising an inlet end and a discharge end, and a slurry passageway extending through the nozzle from the inlet end to the discharge end for passage of the slurry into the flash tank from a location outside the flash tank, the slurry passageway comprising a choke comprising a zone of the passageway in which its cross-sectional area is the smallest, the passageway flaring with respect to the axis thereof toward said discharge end to define an expansion cone, the choke cross-sectional area is determined by a function relating mass flow rate of slurry through the nozzle and pressure within the nozzle, and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle consisting of a straight choke;

wherein the nozzle has a choke diameter of between about 3½ and

about 4½

inches, an expansion cone exit diameter of between about 7 and about 7½

inches, and an expansion cone length of between about 5¾

inches and about 6¼

inches.

12. The process of claim 11 wherein the expansion cone has a half angle of between about 14°

and about 16°

.

14. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising:

an inlet end;

an outlet end;

a tubular passageway extending between the inlet end and the outlet end comprising a choke consisting of a smallest diameter portion of the passageway, and an expansion cone defined by the passageway flaring with respect to the axis thereof toward the outlet end; and

the diameter of the choke and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle wherein the passageway is cylindrical from the narrowest portion to the outlet end.

15. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising:

an inlet end;

an outlet end;

a tubular passageway extending between the inlet end and the outlet end comprising a choke consisting of a smallest diameter portion of the passageway, and an expansion cone defined by the passageway flaring with respect to the axis thereof toward the outlet end; and

the diameter of the choke and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle wherein the passageway is cylindrical from the narrowest portion to the outlet end;

wherein the choke has a diameter between about 2.8 inches and about 4.6 inches, the expansion cone exit diameter is between about 7.7 inches and about 11.5 inches, the expansion cone length is between about 4 and about 8 inches, and the expansion cone has a half angle of between about 20° and

about 32°

.

16. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising:

an inlet end;

an outlet end;

a tubular passageway extending between the inlet end and the outlet end comprising a choke consisting of a smallest diameter portion of the passageway, and an expansion cone defined by the passageway flaring with respect to the axis thereof toward the outlet end; and

the diameter of the choke and the exit diameter of the expansion cone being selected to establish a relationship between pressure upstream of the nozzle and pressure in the flash tank so that shock waves inside the flash tank are weaker than shock waves inside a reference flash tank having identical dimensions and configuration and operating under identical conditions except having a reference pressure let down nozzle wherein the passageway is cylindrical from the narrowest portion to the outlet end;

wherein the nozzle has a choke diameter of between about 3½ and

about 4½

inches, the expansion cone exit diameter is between about 7 and about 7½

inches, the expansion cone length is between about 5¾

inches and about 6¼

inches, and the expansion cone has a half angle of between about 14° and

about 16°

.

17. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising:

an inlet end;

an outlet end;

a tubular passageway extending between the inlet end and the outlet end comprising a choke consisting of a smallest diameter portion of the passageway, and an expansion cone defined by the passageway flaring with respect to the axis thereof toward the outlet end;

the diameter of the choke being determined by the mass flow rate of the slurry through the nozzle and pressure within the nozzle; and

the exit diameter of the expansion cone being selected so that the pressure of the slurry at the outlet end is about the same as the pressure in the flash tank.

18. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising:

an inlet end;

an outlet end;

a tubular passageway extending between the inlet end and the outlet end comprising a choke consisting of a smallest diameter portion of the passageway, and an expansion cone defined by the passageway flaring with respect to the axis thereof toward the outlet end;

the diameter of the choke being determined by the mass flow rate of the slurry through the nozzle and pressure within the nozzle; and

the exit diameter of the expansion cone being selected so that the pressure of the slurry at the outlet end is about the same as the pressure in the flash tank;

wherein the choke has a diameter between about 2.8 inches and about 4.6 inches, the expansion cone exit diameter is between about 7.7 inches and about 11.5 inches, the expansion cone length is between about 4 and about 8 inches, and the expansion cone has a half angle of between about 20° and

about 32°

.

19. A wear-resistant flash tank pressure let down nozzle for use in passing an ore slurry into an ore slurry flash tank to release steam from the slurry and reduce the pressure of the slurry, the nozzle comprising:

an inlet end;

an outlet end;

a tubular passageway extending between the inlet end and the outlet end comprising a choke consisting of a smallest diameter portion of the passageway, and an expansion cone defined by the passageway flaring with respect to the axis thereof toward the outlet end;

the diameter of the choke being determined by the mass flow rate of the slurry through the nozzle and pressure within the nozzle; and

the exit diameter of the expansion cone being selected so that the pressure of the slurry at the outlet end is about the same as the pressure in the flash tank;

wherein the nozzle has a choke diameter of between about 3½ and

about 4½

inches, the expansion cone exit diameter is between about 7 and about 7½

inches, the expansion cone length is between about 5¾

inches and about 6¼

inches, and the expansion cone has a half angle of between about 14° and

about 16°

.